A non-woven fiber mat for lead-acid batteries is provided. The non-woven fiber mat includes glass fibers coated with a sizing composition, a binder composition, and organic active compounds, wherein the organic active compounds are effective in reducing or preventing sulphation in lead-acid batteries.
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1. A non-woven fiber pasting mat comprising:
a plurality of fibers coated with a sizing composition, wherein the sizing composition comprises a film former selected from a group consisting of polyvinyl acetates, polyurethanes, modified polyolefins, polyesters epoxides, and mixtures thereof; and
a binder composition comprising one or more organic active compounds, said organic active compounds comprising one or more of sulphosuccinate (di-octyl);
polyvinylalcohol; colloidal silica; polyacrylamide; phosphonic acid; polyacrylic acid;
phosphate ester; polycarboxylic acid; polymeric anionic compounds;
hexamethylenediaminetetrakis; chitin; chitosan; inulin; polyaspartic acid;
polysuccinimide; iminodisuccinate; maleic acid/acrylic acid copolymer; maleic acid/acrylamide copolymer; humic acid; calcium salt of polymers from naphtalenenesulphonic acid condensed with formaldehyde; sodium salt of condensed sulfonated naphtalene; perfluoroalkylsulfonic acid; and cellulose,
wherein the binder composition holds the fibers together to form a non-woven mat,
wherein said organic active compounds are present in the binder composition in an amount from about 0.05 to about 25.0 wt. % of said binder composition, and
wherein said organic active compounds are operable to reduce sulphation in a lead-acid battery.
24. A non-woven retainer mat for contacting a separator in a lead-acid battery comprising:
a plurality of fibers coated with a sizing composition, wherein the sizing composition comprises a film former selected from a group consisting of polyvinyl acetates, polyurethanes, modified polyolefins, polyesters epoxides, and mixtures thereof; and
a binder composition comprising one or more organic active compounds, said organic active compounds comprising one or more of sulphosuccinate (di-octyl);
polyvinylalcohol; colloidal silica; polyacrylamide; phosphonic acid; polyacrylic acid;
phosphate ester; polycarboxylic acid; polymeric anionic compounds;
hexamethylenediaminetetrakis; chitin; chitosan; inulin; polyaspartic acid;
polysuccinimide; iminodisuccinate; maleic acid/acrylic acid copolymer; maleic acid/acrylamide copolymer; humic acid; calcium salt of polymers from naphtalenenesulphonic acid condensed with formaldehyde; sodium salt of condensed sulfonated naphtalene; perfluoroalkylsulfonic acid; and cellulose,
wherein the binder composition holds the fibers together to form a non-woven mat, and
wherein said organic active compounds are present in the binder composition in an amount from about 0.05 to about 25.0 wt. % of said binder composition, and
wherein said organic active compounds are operable to reduce sulphation in a lead-acid battery.
22. A method of forming a non-woven fiber mat for use in a lead-acid battery, said method comprising:
dispersing a plurality of fibers into an aqueous slurry, said fibers being coated with a sizing composition, wherein the sizing composition comprises a film former selected from a group consisting of polyvinyl acetates, polyurethanes, modified polyolefins, polyesters epoxides, and mixtures thereof;
depositing said slurry onto a screen;
applying a binder onto the deposited slurry; and
heating said binder-coated slurry, thereby curing said binder coated slurry and forming a non-woven fiber mat, wherein said fiber mat includes one or more organic active compounds included in said binder in an amount from about 0.05 to about 25.0 wt. % of said binder, said organic active compounds comprising one or more of sulphosuccinate (di-octyl); polyvinylalcohol; colloidal silica; polyacrylamide; phosphonic acid; polyacrylic acid; phosphate ester; polycarboxylic acid; polymeric anionic compounds; hexamethylenediaminetetrakis; chitin; chitosan; inulin; polyaspartic acid;
polysuccinimide; iminodisuccinate; maleic acid/acrylic acid copolymer; maleic acid/acrylamide copolymer; humic acid; calcium salt of polymers from naphtalenenesulphonic acid condensed with formaldehyde; sodium salt of condensed sulfonated naphtalene; perfluoroalkylsulfonic acid; and cellulose.
13. A lead-acid battery comprising:
a positive electrode having a first face and a second face opposite said first face and a negative electrode having a first face and a second face opposite said first face, wherein each of said positive and negative electrode is immersed within an electrolyte;
a non-woven fiber pasting mat at least partially covering a surface of at least one of said first and second faces of at least one of said positive and said negative electrode, said non-woven fiber pasting mat comprising:
a plurality of fibers coated with a sizing composition, wherein the sizing composition comprises a film former selected from a group consisting of polyvinyl acetates, polyurethanes, modified polyolefins, polyesters epoxides, and mixtures thereof; and
a binder composition comprising one or more organic active compounds, said organic active compounds comprising one or more of sulphosuccinate (di-octyl);
polyvinylalcohol; colloidal silica; polyacrylamide; phosphonic acid; polyacrylic acid;
phosphate ester; polycarboxylic acid; polymeric anionic compounds;
hexamethylenediaminetetrakis; chitin; chitosan; inulin; polyaspartic acid;
polysuccinimide; iminodisuccinate; maleic acid/acrylic acid copolymer; maleic acid/acrylamide copolymer; humic acid; calcium salt of polymers from naphtalenenesulphonic acid condensed with formaldehyde; sodium salt of condensed sulfonated naphtalene; perfluoroalkylsulfonic acid; and cellulose,
wherein the binder composition holds the fibers together to form a non-woven mat, and
wherein said organic active compounds are present in the binder composition in an amount from about 0.05 to about 25.0 wt. % of said binder composition, and wherein said organic active compounds reduce formation of lead sulphate on said negative electrode.
2. The non-woven fiber pasting mat of
3. The non-woven fiber pasting mat of
4. The non-woven fiber pasting mat of
6. The non-woven fiber pasting mat of
7. The non-woven fiber pasting mat of
8. The non-woven fiber pasting mat of
9. The non-woven fiber pasting mat of
10. The non-woven fiber pasting mat of
11. The non-woven fiber pasting mat of
12. The non-woven fiber pasting mat of
14. The lead-acid battery of
15. The lead-acid battery of
16. The lead-acid battery of
17. The lead-acid battery of
18. The lead-acid battery of
19. The lead-acid battery of
20. The lead-acid battery of
21. The lead-acid battery of
23. The method of
25. The non-woven retainer mat of
26. The non-woven retainer mat of
27. A lead-acid battery comprising:
a positive electrode, a negative electrode, and a separator, having a first face and a second face opposite thereto, disposed therebetween, wherein each of said positive electrode, negative electrode, and separator is immersed within an electrolyte; and
a non-woven retainer mat according to
28. The lead-acid battery of
29. The non-woven retainer mat for contacting a separator in a lead-acid battery of
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The present application is the U.S. national stage entry of PCT/US15/36142, filed on Jun. 17, 2015, which claims priority to U.S. provisional application no. 62/013,097, filed on Jun. 17, 2014, both of which are hereby incorporated by reference in their entirety.
The general inventive concepts relate to lead-acid batteries, and more particularly to non-woven fiber mats for use in lead-acid batteries. The non-woven fiber mats reduce the occurrence of sulphation in lead-acid batteries.
Lead-acid batteries are among the most commonly used rechargeable batteries due to their ability to supply high currents, while having a relatively low production cost. Lead-acid batteries are largely used in the automotive starting, lighting, and ignition (SLI) sector and in other industrial sectors due to their high discharge capability. Conventional lead-acid batteries include a positive electrode (PbO2 plate) and a negative electrode (spongy Pb plate) immersed in a sulfuric acid electrolyte. A separator may be disposed between the positive and negative plates. Separators function to not only provide mechanical separation between the positive and negative plates, but to also prevent shorting between electrodes and allow ionic conduction. There are many different forms of electrodes. In some instances, the electrodes consist of lead or lead alloy plates having a grid-like structure. An active material paste consisting of lead oxides and sulfuric acid may be used to fill the holes in the grid of the positive plate. The active material paste is porous, thereby allowing the acid to react with the lead inside the plate, which increases the surface area of the electrodes. The paste is dried and the positive and negative electrodes are activated by an electrochemical process.
During discharge, both the positive and negative plates react with the acid electrolyte material causing lead (II) sulfate (PbSO4) to coat the plates. Lead sulfate is a soft material that can be re-converted back into lead and sulfuric acid, provided the discharged battery is reconnected to a battery charger in a timely manner. As current is applied to re-charge a lead-acid battery, the lead sulfate partially reverses back to lead and lead oxide. This partial reversal to their original states “recharges” the positive and negative electrodes.
If a lead-acid battery is left in the discharged state for a prolonged period of time, the lead sulfate will begin to form hard crystals and coat the surface of the electrode plates. Such a period of prolonged lead sulfate exposure may occur, for instance, when a lead-acid battery is deprived of a full charge. Because hard lead sulfate is a non-conductive material, when it coats the electrode plates, it causes a reduction in the area needed for the electro-chemical reactions. Additionally, the large crystals can reduce the battery's active material that is responsible for high capacity and low resistance.
There have been numerous attempts to reduce detrimental sulphation in lead-acid batteries. For example, paper has been applied to the plate to control the active material on the grid. For example, traditionally, a cellulosic paper may be applied to the plates to aid in spreading the active material paste, keep moisture in the plate prior to drying and to keep the paste on the grid prior to assembling the battery. However, due to the interference of the pasting paper with the battery performance, the paper is either discarded prior to assembly of the battery or degrades during use. This often causes a disruption in the operation of the battery by interfering with the chemical reactions and/or clogging the electrodes.
Various aspects of the general inventive concepts are directed to a non-woven fiber pasting mat for lead-acid batteries. The non-woven fiber pasting mats include a plurality of glass fibers coated with a sizing composition, a binder composition, and one or more organic active compounds. In some exemplary embodiments, the organic active compounds reduce sulphation in lead-acid batteries.
In some exemplary embodiments, the organic active compounds are included in at least one of the sizing composition and the binder composition.
In some exemplary embodiments, the organic active compounds comprise one or more of sulphosuccinate (di-octyl); polyvinylalcohol; colloidal silica; polyacrylamide; phosphonic acid; polyacrylic acid, such as polycarboxylate and anionic polyelectolyte; phosphate ester; polycarboxylic acid, such as acrylic, maleic, lactic, tartaric, etc.; polymeric anionic compounds, such as polyvinylsulphonic acid and poly(meth)acrylic acid; hexamethylenediaminetetrakis; chitin; chitosan; inulin; polyaspartic acid; polysuccinimide; iminodisuccinate; maleic acid/acrylic acid copolymer; maleic acid/acrylamide copolymer; humic acid; calcium salt of polymers from naphtalenenesulphonic acid condensed with formaldehyde; sodium salt of condensed sulfonated naphtalene; perfluoroalkylsulfonic acid; and cellulose.
Various aspects of the general inventive concepts are directed to a lead-acid battery that includes at least one positive electrode and at least one negative electrode immersed within an electrolyte and a non-woven glass fiber pasting mat at least partially covering a surface of at least one of the positive and negative electrode. The non-woven fiber pasting mat includes a plurality of glass fibers coated with a sizing composition, a binder composition, and one or more organic active compounds. In some exemplary embodiments, the organic active compounds reduce formation of lead sulphate on said negative electrode.
In some exemplary embodiments, said organic active compounds are included in at least one of the sizing composition and the binder composition.
Various exemplary embodiments of the general inventive concepts are further directed to a method of forming an anti-sulphation pasting mat for use in a lead-acid battery. The method includes dispersing a plurality of glass fibers into an aqueous slurry, said glass fibers being coated with a sizing composition; depositing the slurry onto a moving screen; applying a binder onto the deposited slurry; and heating the binder-coated slurry, thereby curing the binder and forming a non-woven pasting mat. The pasting mat includes one or more organic active compounds included in at least one of the sizing composition and the binder.
In some exemplary embodiments, the non-woven fiber pasting mat is capable of increasing the life cycle of a lead-acid battery by at least 10% compared to an otherwise comparable battery without the pasting mat.
Additional features and advantages will be set forth in part in the description that follows, and in part may be obvious from the description, or may be learned by practice of the exemplary embodiments disclosed herein. The objects and advantages of the exemplary embodiments disclosed herein will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing summary and the following detailed description are exemplary and explanatory only and are not restrictive of the general inventive concepts as disclosed herein or as claimed.
Example embodiments of the invention will be apparent from the more particular description of certain example embodiments of the invention provided below and as illustrated in the accompanying drawings.
Various exemplary embodiments will now be described more fully, with occasional reference to any accompanying drawings. These exemplary embodiments may, however, be embodied in different forms and should not be construed as limited to the descriptions set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will convey the general inventive concepts to those skilled in the art.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which these exemplary embodiments belong. The terminology used in the description herein is for describing particular exemplary embodiments only and is not intended to be limiting of the exemplary embodiments.
As used in the specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety.
Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present exemplary embodiments. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed in light of the number of significant digits and ordinary rounding approaches.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the exemplary embodiments are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Every numerical range given throughout this specification and claims will include every narrower numerical range that falls within such broader numerical range, as if such narrower numerical ranges were all expressly written herein.
The general inventive concepts relate to a non-woven fiber mat, such as a pasting mat or a retainer mat, or other batteries. The non-woven fiber mat may comprise a plurality of reinforcement fibers combined in the form of a sheet. In some exemplary embodiments, the reinforcement fibers are made from glass. However, the reinforcement fibers may also include synthetic fibers, or a combination of glass fibers and synthetic fibers. The term synthetic fiber, as used herein, is intended to include any man-made fiber having suitable reinforcing characteristics including fibers made from suitable polymers such as, for example, polyesters, polyolefins, nylons, aramids, poly(phenylene sulfide), and suitable non-glass fibers such as, carbon, silicon carbide (SiC) and boron nitride.
The glass fibers may be formed from any type of glass suitable for a particular application and/or desired product specifications, including conventional glasses. Non-exclusive examples of glass fibers include A-type glass fibers, C-type glass fibers, G-type glass fiber, E-type glass fibers, S-type glass fibers, E-CR-type glass fibers (e.g., Advantex® glass fibers commercially available from Owens Corning), R-type glass fibers, wool glass fibers, biosoluble glass fibers, and combinations thereof, which may be used as the reinforcing fiber. In some exemplary embodiments, the glass fibers are durable in an acidic environment.
The non-woven glass fiber mat may comprise a single mat, or more than one mat, e.g., two, three, four, or five mats, which may be employed in a single lead-acid battery. Each non-woven glass fiber mat may comprise a single layer, or may be composed of more than one layer, e.g., two, three, four, or five layers. In some exemplary embodiments, the non-woven fiber mat comprises a non-woven glass fiber pasting mat. In some exemplary embodiments, the non-woven fiber mat comprises a non-woven glass fiber retainer mat.
In some exemplary embodiments, the glass fibers have a diameter that is at least 0.2 microns, such as from 0.2 to 30 microns. In some exemplary embodiments, the glass fibers have a diameter from about 1 to about 25 microns, or from about 6 to about 23 microns.
Glass fibers may be formed by drawing molten glass into filaments through a bushing or orifice plate and applying a sizing composition to the filaments as they solidify. The sizing composition provides protection to the fibers from interfilament abrasion and promotes compatibility between the glass fibers and the matrix in which the glass fibers are to be used. After the sizing composition is applied, the fibers may be gathered into one or more strands and wound into a package or, alternatively, the fibers may be chopped while wet with the sizing and collected. The collected chopped strands may then be dried to form dry chopped fibers or they can be packaged in their wet condition as wet chopped fibers.
In some exemplary embodiments, the sizing compositions used to coat glass fibers are aqueous-based compositions, such as suspensions or emulsions. The suspension or emulsion has a solids content that may be composed of one or more of a film former, a coupling agent, a lubricant, and a surfactant. A film former may work to hold individual filaments together to form fibers, and protect the filaments from damage caused by abrasion. Acceptable film formers include, for example, polyvinyl acetates, polyurethanes, modified polyolefins, polyesters epoxides, and mixtures thereof. A coupling agent may be included in a sizing composition to enhance the adhesion of the sizing composition with a matrix material when forming a composite, to improve the composite properties. In some exemplary embodiments, the coupling agent is an organofunctional silane.
Additional additives may be included in the sizing compositions, depending on the intended application. Such additives include, for example, anti-statics, wetting agents, antioxidants, and pH modifiers.
In accordance with the general inventive concepts, the non-woven glass fiber mat may be produced using either continuous or chopped fibers, or a combination of the continuous and chopped fibers. The chopped fibers or fiber strands have lengths that may vary depending on a particular process and/or application. In some exemplary embodiments, the chopped fibers/strands have a length of about 3 to about 60 mm.
The non-woven glass fiber mats may be formed in accordance with any of the known methods for producing glass fiber mats, such as wet-laid processing and dry-laid processing. In a wet-laid processing, a water slurry (i.e., “whitewater”) is provided into which glass fibers are dispersed. The white water may contain dispersants, viscosity modifiers, defoaming agents or other chemical agents. The slurry containing the glass fibers is then deposited onto a moving screen and a substantial amount of the water is removed. A binder may then be applied to the deposited fibers and the resulting mat is dried to remove any remaining water and to cure the binder, framing a non-woven glass fiber mat. In a dry-laid process, fibers are chopped and air blown onto a conveyor and a binder is then applied to form a mat. Dry-laid processes may be particularly suitable for the production of highly porous mats having bundles of glass fibers.
The binder may be any type of binder composition, such as an acrylic binder, a styrene acrylonitrile binder, a styrene butadiene rubber binder, a urea formaldehyde binder, an epoxy binder, a polyurethane binder, a phenolic binder, a polyester binder, or mixtures thereof. Exemplary acrylic binders may include, for example, polyacrylic acid, ethylacrylate, methacrylate, methylmethacrylate, styrene acrylate, or mixtures thereof. In some exemplary embodiments, the binder is a thermoset acrylic binder formed of polyacrylic acid and at least one polyol, such as for example, triethanolamine or glycerine. The binder may optionally contain one or more additives for improving processibility and/or product performance. Non-limiting examples of such additives include dyes, oils, fillers, colorants, UV stabilizers, coupling agents (for example, aminosilanes), lubricants, wetting agents, surfactants, antistatic agents, and combinations thereof.
In some exemplary embodiments, the binder comprises about 1 to about 30 weight percent of the total dry weight of the glass fiber mat. In other exemplary embodiments, the binder comprises about 8 to about 25 weight percent of the total dry weight of the glass fiber mat. In some exemplary embodiments, the binder comprises about 18 to 25 weight percent of the total dry weight of the glass fiber mat.
In some exemplary embodiments, the non-woven glass fiber mats are treated with one or more organic active compounds that are capable of reducing or eliminating sulphation of the electrodes in a lead-acid battery. The organic active compounds may be included as additives to the sizing composition, additives to the binder composition, or as an additive to both the sizing and binder compositions. In some exemplary embodiments, the additives may be added to the surface of the mat, after the mat has been formed.
In some exemplary embodiments, the organic active compounds include active ingredients that directly influence the reactions that take place on the surface of an electrode. In some exemplary embodiments, the organic active compounds include one or more of sulphosuccinate (di-octyl); polyvinylalcohol; colloidal silica; polyacrylamide; phosphonic acid; polyacrylic acid, such as polycarboxylate and anionic polyelectolyte; phosphate ester; polycarboxylic acid, such as acrylic, maleic, lactic, tartaric, etc.; polymeric anionic compounds, such as polyvinylsulphonic acid and poly(meth)acrylic acid; hexamethylenediaminetetrakis; chitin; chitosan; inulin; polyaspartic acid; polysuccinimide; iminodisuccinate; maleic acid/acrylic acid copolymer; maleic acid/acrylamide copolymer; humic acid; calcium salt of polymers from naphtalenenesulphonic acid condensed with formaldehyde; sodium salt of condensed sulfonated naphtalene; perfluoroalkylsulfonic acid; and cellulose. In some exemplary embodiments, the organic active ingredients include one or more of sulphosuccinate (di-octyl) and a polyvinylalcohol/colloidal silica compound.
The organic active compounds are capable of reacting directly with lead sulfate that forms during discharge of a lead-acid battery. Sulphation is primarily an issue on the negative plates, where sulphation deteriorates the negative electrode properties. By reacting with the lead sulfate, the organic active compounds keep the lead sulfate soluble in the sulfuric acid electrolyte, which may at least delay, and in some cases inhibit or otherwise reduce, the formation of lead sulfate crystals. In some exemplary embodiments, the use of organic active compounds as described herein prevents the formation of lead sulfate crystals.
In some exemplary embodiments, the organic active compounds are present in the non-woven mat in an amount from about 0.05 to about 25.0 weight percent of said binder and/or sizing composition containing the organic compounds. In other exemplary embodiments, said organic active compounds are present in an amount from about 0.1 to about 20 weight percent of said binder or sizing composition containing the organic active compounds.
In some exemplary embodiments, the binder itself may act as an anti-sulphation composition. For example, a polyacrylic acid binder may also react directly with the lead sulphate to maintain its solubility in the electrolyte. Accordingly, in some exemplary embodiments, 100% (or substantially all) of the binder will comprise surface active chemistry.
By incorporating the organic active compounds directly into the sizing composition and/or into the binder composition, the organic active compounds are directly exposed to the surface of the electrodes where lead sulphate crystals form. The organic active compounds have a limited solubility in the acid electrolyte and are released slowly during use once the non-woven mat is in the acid electrolyte and the plates become active. Utilizing the non-woven fiber mat as a pasting mat allows for the slow release of the organic active compounds from the pasting mat allows the organic active compounds to achieve direct contact with the surface of the electrodes. The solubility of the organic active compounds in the acid electrolyte may be affected by the temperature, as fairly high temperatures are reached in battery curing and formation. The high temperatures may initiate leaching from the pasting mat to the surface of the negative electrode.
The organic active compounds are prone to oxidation, which is undesirable as oxidation may destroy their anti-sulphation activity and their oxidation products may be harmful for the battery. Oxidation of the organic active compounds mainly takes place at the positive plate because lead dioxide (PbO2) is a very strong oxidizer, especially in combination with sulphuric acid. By applying the organic active compounds to the negative plate via the non-woven pasting mat, the distance to the positive plate is maximized and the organic active compounds have a lower risk of oxidation at the positive plate compared to applications that introduce chemistries directly into the electrolyte.
In some exemplary embodiments, treating the electrode surface with organic active compounds by incorporating one or more organic active compounds into the., sizing composition and/or binder composition of a pasting mat demonstrates an improvement in battery life cycle of at least 10%, or at least about 25% over otherwise similar lead-acid battery cells that either have no pasting mat or include a cellulose base pasting mat.
The process of preparing a lead-acid battery comprises forming one or more battery cells, which each include a positive plate electrode having a first face and a second face, opposite the first face, a negative plate electrode having a first face and a second face, opposite the first face, and a separator disposed therebetween. The positive electrode includes a grid containing lead alloy material. A positive active material, such as lead dioxide, is coated on the grid of the positive electrode. The negative plate electrode also includes a grid of lead alloy material that is coated with a negative active material, such as lead. The positive and negative plate electrodes are immersed in an electrolyte that may include sulfuric acid and water. The separator may be positioned between the positive and negative plate electrodes to physically separate the two electrodes while enabling ionic transport.
The non-woven fiber pasting mat disclosed herein may be positioned to partially or fully cover at least one surface of the negative plate electrode. In some exemplary embodiments, pasting mats are positioned on each side of the negative plate electrode. In some exemplary embodiments, the use of glass fibers in the non-woven pasting mat provides added dimensional stability to the negative plates during charge and discharge. During discharge the negative plates generally increase in volume and then shrink significantly during a charging cycle, due to the different crystals formed. The improved dimensional stability provided by the glass fiber pasting mat reduces this expansion/shrinkage, which in turn leads to an improved battery life by preventing active mass from shedding from the grid and maintaining good contact between the active material and the grid to ensure charge acceptance and current flow. In some exemplary embodiments, a non-woven fiber pasting mat is positioned to partially or fully cover at least one surface of the positive plate, to function as a retainer by holding the active material in place on the positive plate while also providing improved dimensional stability. In some exemplary embodiments, pasting mats are positioned on each side of the positive plate electrode. In some exemplary embodiments, non-woven fiber pasting mats are positioned on both sides of each of the positive and negative plates.
In other exemplary embodiments, the non-woven fiber mat functions as a retainer mat and is positioned in contact with at least one side of the separator.
The following examples are meant to better illustrate the present invention but are not intended to limit the general inventive concepts in any way.
A variety of 20 hour rate 2 Volt battery cells were assembled and the negative plates were joined with non-woven glass fiber pasting mats having different binder and/or fiber compositions. The cells were then subjected to partial state of charge cycling tests and afterwards submitted to teardown analysis. The presence of crystallized lead sulfate was determined on the top and the bottom of the plate with wet analysis and x-ray diffraction.
A) Partial State of Charge (PSoC) Testing Method:
The partial state of charge cycle testing procedure repeats a partial discharge and charge to an amount of capacity around various levels of the average state of charge. An equalization step in the PSoC test method was omitted to increase the partial state of charge residence time and to increase the test speed. The battery cells were subjected to cycling at 17.5% Depth of Discharge (DoD) at 27° C. with an initial point of cycling at 50% State of Charge (SoC). The cycling conditions included preconditioning by discharge for 2.5 hours at 4×120A (4A), reaching the initial point of cycling at 50% SoC. The batteries were then charged for 40 minutes at Imax=7A (7×I20A) and Umax=2.4V/Cell. The batteries were then discharged for 30 minutes at 7A (7×I20A). The consecutive charge and discharge constituted one cycle. The higher number of cycles indicates a longer battery life time. After reaching the switch-off criteria (Ucell≤1.666V), the cycling ended and the cell was charged and submitted to a detailed tear down analysis.
B) Tear-Down Analysis:
To perform the tear down analysis, the negative plate was divided into three sections: top, middle, and bottom. The active material from the top and bottom of the plate was separately selected at different places and grinded to homogenize the sample.
The same homogenized sample of top and bottom negative plate active material was used to record an X-ray diffraction pattern. The device used to record the X-ray diffraction pattern was a Philips 2134, ADP-15.
The active material on the top and bottom sections was further analyzed for PbSO4 and Pb content from the final recharge. The PbSO4 weight percent is considered irreversible lead sulphate, indicative of sulphation. Additionally, if the battery has suffered from sulphation, the PbSO4 would be concentrated on the bottom of the plate.
TABLE 1
Battery Sulphation
PbSO4 located at
PbSO4 located at
# of
top of negative
bottom of negative
cycles
plate after final
plate after final
Organic active
at PSoC
recharge.
recharge.
Sample
chemistry
cycling
(wt. %)
(wt. %)
Comments
Comp.
None
271
11%
65%
Commercially
Sample 1
available glass
pasting mat
(acrylic bound
glass tissue),
strong
sulphation
Comp.
None
410
21%
57%
Conductive
Sample 2
carbon fiber
added, strong
sulphation
Sample 3
Sulphosuccinate
874
5%
18%
Low sulphation
(di-octyl)
Sample 4
Polyvinylalcohol/
579
9%
11%
Low sulphation
colloidal silica
As illustrated in Table 1, comparative samples 1 and 2, which included conventional pasting mats without organic active compounds, demonstrated significant sulphation at the bottom of the negative plate. Comparatively, Examples 3 and 4, including organic active compounds, demonstrated significantly lower sulphation of less than 10% and also increased partial state of charge cycling to greater than 500 cycles, which is indicative of a higher battery life.
Specifically, Sample 3 included a 25 g/m2 pasting mat comprising a mixture of 6.5 μm-6 mm and 11 μm-13 mm chopped glass fibers. The mat was bonded with a self-crosslinkable acrylic based binder. The mat had a binder content of about 20%. A di-octylsuphosuccinate surfactant was added to the binder in about 0.2 weight percent based on dry binder solids. Example 4 included a 45 g/m2 pasting mat comprising a base tissue formed of a 50/50 mixture of 6.5 μm-6 mm glass fibers and 11 μm-6 mm glass fibers and included about 16 weight percent of a polyvinylalcohol binder. The base sheet was treated with a mixture of self cross-linkable acrylate and colloidal silica. The final mat included about 3 g/m2 polyvinylalcohol and 22 g/m2 colloidal silica.
A variety of non-woven fiber pasting mats were prepared to have various fiber types, weights, and thicknesses. Table 2 below illustrates the properties of the mats.
TABLE 2
Properties of Fiber Mats
Air
LOI
Fiber
Weight
Thickness
permeability
measured
Electrical
ER/0.1
Sample
type
(grams/m2)
(mm)
(l/m2s)
(%)
Resistance
mm
1
glass
25.1
0.19
7420
12.0
11.7
6.17
2
glass
22.9
0.205
6780
21.1
13.7
6.66
3
glass
24.6
0.22
8330
16.5
16.3
7.43
4
glass
24.2
0.165
5190
18.9
14.1
8.53
5
glass
131.5
0.9
2400
14.1
37.8
4.20
6
glass
105.3
0.95
4420
15.7
27.1
2.85
7
glass
117.3
0.84
2400
14.7
36.7
4.36
8
glass
23.8
0.19
6930
23.0
13.8
7.24
9
glass
23.5
0.2
7650
11.9
12.0
6.02
10
glass
84.5
0.61
3130
15.9
26.0
4.26
11
glass
53.8
0.42
4020
17.8
30.1
7.16
12
glass
39.7
0.33
5130
18.9
23.1
7.01
12
glass
69.1
0.38
1790
18.2
26.0
6.85
13
glass
48.2
0.42
4246
11.6
19.6
4.66
14
glass
41.8
0.4
4488
18.8
15.4
3.84
15
glass
47.5
0.42
4114
27.9
24.3
5.78
16
glass
51
0.42
3982
33.5
46.2
11.01
17
glass
40.3
0.41
5104
16.9
14.2
3.46
18
glass
43.7
0.41
4378
19.4
14.0
3.41
19
glass
43.6
0.41
3740
20.1
22.0
5.37
20
glass
50.1
0.41
1606
19.8
21.8
5.33
21
glass
39.6
0.4
5786
15.4
7.7
1.94
Comparative
polyester
25
0.06
1570
100.0
26.9
44.77
Example-1
Comparative
polyester
18.5
0.08
2850
100.0
19.7
24.59
Example-2
Comparative
glass
19.5
0.17
5540
38.0
26.1
15.37
Example -3
As illustrated in Table 2, the electrical resistance for the non-woven fiber mats was lowest for glass fiber mats prepared in accordance with the present invention. The electrical resistance, when normalized over 0.10 mm thickness, is lowest for the non-woven glass fiber mats prepared in accordance with the present invention. Each of samples 1-21 demonstrates electrical resistance, normalized over 0.1 mm, of lower than 15/0.1 mm. In some exemplary embodiments, the glass fibers may have an electrical resistance of less than 10/0.1 mm. The normalized electrical resistances of the examples illustrated in Table 2 are further compared in
Although the general inventive concepts have been set forth in what is believed to be exemplary illustrative embodiments, a wide variety of alternatives would be known or otherwise apparent to those of skill in the art and, thus, are encompassed by the general inventive concepts. The general inventive concepts are not otherwise limited, except for the recitation of the claims set forth below.
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